It is intended to investigate experimentally (in rhesus monkeys) and pathologically retinal, optic nerve head, and uveal vascular disorders. In (a) ischemic, (b) hemorrhagic, and (c) venous stasis retinopathy, it is our intention to study (1) the time required for the retinal ischemia to produce functional and anatomical deaths in the retina and its various components, and various factors influencing this; (2) the natural history, pathology and pathogenesis of various retinal vascular diseases in a detailed prospective experimental study; and (3) the evolution of the retinal vascular dynamics. The uveal circulation in health and disease will be investigated systematically to determine (a) its anatomy, (b) its dynamics in health and in various occlusive disorders, (c) the ocular lesions produced by occlusion of various ciliary vessels, and (d) the role of the posterior ciliary ischemia in glaucoma, low-tension glaucoma, and anterior ischemic optic neuropathy. In addition to these, other circulatory disorders of the optic nerve head will be investigated. In all these studies, the assessment will be made (1) for the various ocular lesions, (2) for the circulatory dynamics by perfusion and fluorescein angiography, (3) for retinal functions by electrophysiological testing, and (4) for pathological changes by histological and electron microscopical examination. BIBLIOGRAPHIC REFERENCES: Hayreh, S.S., Hayreh, M.S.: Optic disc edema in raised intracranial pressure II. Early detection with fluorescein fundus angiography and stereoscopic color photography. Arch. Ophthal. (Chicago) 1977, in press. Tso, M.O.M., Hayreh, S.S.: Optic disc edema in raised intracranial pressure. III. Pathological studies. Arch. Ophthal. (Chicago) 1977, in press.